Subscribe to Spaceflight Now Plus for access to our extensive video collections!How do I sign up?Video archiveSTS-69: The Dog CrewAstronauts flying aboard shuttle Endeavour in September 1995 called themselves the Dog Crew, a lighthearted twist to their complicated mission to launch and then retrieve a pair of satellites.PlayRiding on EndeavourNow you can take a virtual trip aboard shuttle Endeavour's recent launch thanks to video cameras mounted inside the ship's cockpit as well as outside on the twin solid rocket boosters and external tank.Full CoverageLaunch of PhoenixThe Phoenix lander bound for the northern plains of Mars is launched atop a Delta 2 rocket from Cape Canaveral.Full coveragePhoenix animationProject officials narrate animation of Phoenix's launch from Earth, arrival at Mars, touchdown using landing rockets and the craft's robot arm and science gear in action.Play"The Time of Apollo"This stirring 1970s documentary narrated by Burgess Meredith pays tribute to the grand accomplishments of Apollo as men left Earth to explore the Moon and fulfill President Kennedy's challenge to the nation.Play"Apollo 17: On The Shoulders of Giants"Apollo's final lunar voyage is relived in this movie. The film depicts the highlights of Apollo 17's journey to Taurus-Littrow and looks to the future Skylab, Apollo-Soyuz and shuttle programs.Play"Apollo 10: To Sort Out The Unknowns"The May 1969 mission of Apollo 10 served as a final dress rehearsal before the first lunar landing later that summer. Stafford, Young and Cernan went to the moon to uncover lingering spacecraft problems that needed to be solved.PlayTraveling on Freedom 7Fly with Alan Shepard during his historic journey into space with this documentary that takes the viewer along as an invisible companion to America's first astronaut.PlayBecome a subscriberMore video

PASADENA, Calif. - Scientists on the Cassini mission to Saturn are poring through hundreds of images returned from the Sept. 10 flyby of Saturn's two-toned moon Iapetus. Pictures returned late Tuesday and early Wednesday show the moon's yin and yang -- a white hemisphere resembling snow, and the other as black as tar.

Images show a surface that is heavily cratered, along with the mountain ridge that runs along the moon's equator. Many of the close-up observations focused on studying the strange 20-kilometer high (12 mile) mountain ridge that gives the moon a walnut-shaped appearance.

"The images are really stunning," said Tilmann Denk, Cassini imaging scientist at the Free University in Berlin, Germany, who was responsible for the imaging observation planning. "Every new picture contained its own charm. I was most pleased about the images showing huge mountains rising over the horizon. I knew about this scenic viewing opportunity for more than seven years, and now the real images suddenly materialized."

This stunning close-up view shows mountainous terrain that reaches about 6 miles high along the unique equatorial ridge of Iapetus. Credit: NASA/JPL/Space Science InstituteDownload larger image version here

This flyby was nearly 100 times closer to Iapetus than Cassini's 2004 flyby, bringing the spacecraft to about 1,640 kilometers (1,000 miles) from the surface. The moon's irregular walnut shape, the mountain ridge that lies almost directly on the equator and Iapetus' brightness contrast are among the key mysteries scientists are trying to solve.

"There's never a dull moment on this mission," said Bob Mitchell, Cassini program manager, NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are very excited about the stunning images being returned. There's plenty here to keep many scientists busy for many years."

"Our flight over the surface of Iapetus was like a non-stop free fall, down the rabbit hole, directly into Wonderland! Very few places in our solar system are more bizarre than the patchwork of pitch dark and snowy bright we've seen on this moon," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute, Boulder, Colo.

Dark material splatters the walls and floors of craters in the surreal, frozen wastelands of Iapetus. This image shows terrain in the transition region between the moon's dark leading hemisphere and its bright trailing hemisphere. Credit: NASA/JPL/Space Science InstituteDownload larger image version here

The return of images and other data was delayed early Tuesday due to a galactic cosmic ray hit which put the spacecraft into a precautionary state called safe mode. This occurred after the spacecraft had placed all of the flyby data on its data recorders and during the first few minutes after it began sending the data home. The data flow resumed later that day and concluded on Wednesday.

The spacecraft is operating normally and its instruments are expected to return to normal operations in a few days.

"Iapetus provides us a window back in time, to the formation of the planets over four billion years ago. Since then its icy crust has been cold and stiff, preserving this ancient surface for our study," said Torrence Johnson, Cassini imaging team member at JPL.

Cassini zooms in, for the first time, on the patchy, bright and dark mountains originally identified in images from the NASA Voyager spacecraft taken more than 25 years earlier. The terrain seen here is located on the equator of Iapetus at approximately 199 degrees west longitude, in the transition region between the moon's bright and dark hemispheres. North is up. Credit: NASA/JPL/Space Science InstituteDownload larger image version here

Cassini's multiple observations of Iapetus will help to characterize the chemical composition of the surface; look for evidence of a faint atmosphere or erupting gas plumes; and map the nighttime temperature of the surface. These and other results will be analyzed in the weeks to come.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C.

The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

Cassini surveys a bright landscape coated by dark material on Iapetus. This image shows terrain in the transition region between the moon's dark leading hemisphere and its bright trailing hemisphere. Credit: NASA/JPL/Space Science InstituteDownload larger image version here